There is an adage that animals can smell our fear: That over-enthusiastic dogs and schadenfreude-loving cats approach people they know are afraid them. A new study has revealed that it’s true – for dogs at least – animals really can smell our fear, and other emotions, and it makes them feel them too.

We already know that our canine companions can interpret visual and auditory cues – they use their puppy dogs eyes just for us, after all, and (depending on how obedient they are) usually come when called.

Now, a study published in Animal Cognition has found that dogs use their sense of smell to attune themselves to their human's emotions and mood, too.

“The role of the olfactory system has been largely underestimated, maybe because our own species is more focused on the visual system,” lead author Biagio D’Aniello from the University of Naples, Italy told New Scientist.

The researchers found that when their owners smelled happy, dogs were more happy and inquisitive, especially around strangers, but when their owners smelled afraid, the dogs exhibited the same behavior and avoided strangers, sticking close to their humans.

How did they manage to separate smell from visual cues though?

Well, it involved a lot of men, sweat, and The Jungle Book.  

D’Aniello and colleagues tested whether dogs could detect emotions by smell alone using a set up of 40 male dog owners, their pets (labradors and golden retrievers), and a stranger.

They had the dog owners watch two films – The Shining and The Jungle Book – to elicit the emotional responses of fear and happiness, respectively, and took sweat samples. Then, they put the owner, their dog, and a stranger in a room, taking it in turns to include a sweat sample from each film, when the human was feeling either fear or happiness, and monitored what happened.

The results revealed the dogs adopted behaviors and stress responses consistent with the emotions that were experienced by the human participants.

When exposed to the fear sweat sample the dogs had a higher heart rate and tended to ignore the stranger, seeking comfort from their owner. With the “happy” odor sample, the dogs appeared more relaxed and less cautious towards the stranger, sniffing them inquisitively.

Although the dogs reacted similarly to how the researchers had expected them to, the dogs’ reactions were notably stronger, showing more signs of stress when they smelled the fear sample.

This study adds to the growing understanding of our faithful companions' emotional capabilities, though whether it's down to the human domestication of dogs, or dogs being innately empathetic is still unknown. Anyway, it's nice to know we're so in tune with our favorite fluffy friends.